Chemical wash compositions for removing drilling fluids

ABSTRACT

Chemical wash compositions comprising a sulfonated lignin and a taurate are provided. In one embodiment, a chemical wash composition is provided comprising water, a sulfonated lignin, and a taurate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 11/424,987filed on the same date herewith, entitled “Method of Using Chemical WashCompositions for Removing Drilling Fluids,” the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to removing a fluid from a well bore witha chemical wash composition, and more particularly, to chemical washcompositions that comprise water, a sulfonated lignin, and a taurate.These chemical wash compositions may be used to remove or substantiallydisplace a drilling fluid from a well bore.

Fluids are often used for a variety of purposes in subterraneanapplications. For instance, a variety of drilling fluids have been usedin drilling subterranean well bores. As used herein, the term “drillingfluid” may refer to any of a number of liquid and gaseous fluids, andmixtures of fluids and solids (as solid suspensions, mixtures andemulsions of liquids, gases and solids) used in operations to drill wellbores into subterranean formations. In some instances, a drilling fluidmay be an aqueous-based fluid that comprises clays and/or polymers.During the drilling of a well bore in a subterranean formation, adrilling fluid may be used to, among other things, cool the drill bit,lubricate the rotating drill string to prevent it from sticking to thewalls of the well bore, prevent blowouts by serving as a hydrostatichead to counteract the sudden entrance into the well bore of highpressure formation fluids, and remove drill cuttings from the well bore.A drilling fluid may be circulated downwardly through a drill pipe anddrill bit and then upwardly through the well bore to the surface.

As the drilling fluid is circulated, a layer of solids referred to as a“filter cake” is formed on the walls of the well bore. The term “filtercake” as used herein may refer to the residue deposited on a permeablemedium when a slurry, such as a drilling fluid, is forced against themedium under a pressure. Filter cake properties such as cake thickness,toughness, slickness and permeability are important because the cakethat forms on permeable zones in the well bore can cause stuck pipe andother drilling problems. Reduced oil and gas production can result fromreservoir damage when a poor filter cake allows deep filtrate invasion.A certain degree of cake buildup usually is desirable to isolateformations from drilling fluids. In openhole completions in high-angleor horizontal holes, the formation of an external filter cake ispreferable to a cake that forms partly inside the formation. The latterhas a higher potential for formation damage. The filter cake and gelledor partially gelled drilling fluid mixed therewith reduce or preventadditional fluid loss as the well is drilled.

Once the well bore has been drilled to a desired depth, the drill stringand drill bit may be removed from the well bore, and a pipe string(e.g., casing, liners, etc.) may be introduced into the well bore. Afterthe pipe string is introduced into the well bore, the well bore may beconditioned by circulating the drilling fluid downwardly through theinterior of the pipe string and upwardly between the annulus of theexterior of the pipe string and the subterranean formation. The purposeof this conditioning, generally, is to remove as much of the filter cakeand gelled or partially gelled drilling fluid from the walls of the wellbore as possible. Unfortunately, however, oftentimes at the end of thisconditioning process, the drilling fluid and filter cake remain on thesurfaces of the well bore and on the pipe string. This can createproblems with subsequent processing, such as in primary cementingoperations, inter alia, because the cement composition is generally notcompatible with the drilling fluid and/or filter cake. Thisincompatibility may result in a lack of bonding between the set cementcomposition and the surfaces in the well bore. This, in turn, may leadto the loss of zonal isolation, as well as other undesirableconsequences.

To mitigate the above-described problem, chemical wash compositionscontaining surfactants and other chemicals have been introduced into thewell bore between the drilling fluid and the cement composition.Chemical washes (also called “preflushes”) and spacer fluids perform thesame functions. The terms “chemical wash” and “chemical washcomposition” as used herein may refer to a fluid, usually water-based,to thin and disperse mud in preparation for cementing. The chemical washmay be pumped ahead of the cement composition to help ensure effectivemud removal and efficient cement placement. As the drilling fluid isdisplaced, the chemical wash contacts the drilling fluid remaining onthe well bore and pipe string surfaces to at least partially remove thedrilling fluid therefrom. Additionally, the chemical wash should also atleast partially remove the filter cake as well. Other specializedchemical washes may be used in the remedial treatment of scales orparaffin deposits in production tubulars.

To mitigate the above-described problem, chemical wash compositionscontaining surfactants and other chemicals have been introduced into thewell bore between the drilling fluid and the cement composition.Chemical washes (also called preflushes) and spacer fluids perform thesame functions. A difference between the two, however, is usuallyrecognized in that a spacer fluid is normally densified by adding amaterial with a fairly high specific gravity such as barite, while apreflush or wash is not so densified. As the drilling fluid isdisplaced, the chemical wash may contact the drilling fluid remaining onthe well bore and pipe string surfaces to at least partially remove thedrilling fluid therefrom. Additionally, the chemical wash should also atleast partially remove the filter cake as well.

A problem associated with current chemical wash compositions is that dueto the chemistry of the compositions, it must be prepared as a liquid,which becomes expensive to ship to remote locations. The currentcompositions may not be dried because they have a low ignition point,and may readily catch fire if the composition is dried.

SUMMARY

The present invention relates to removing drilling fluid from a wellbore with a chemical wash composition and more particularly, to chemicalwash compositions that comprise water, a sulfonated lignin, and ataurate.

In one embodiment, the present invention provides a chemical washcomposition comprising water, a sulfonated lignin, and a taurate.

In another embodiment, the present invention provides a dry chemicalwash composition comprising a sulfonated lignin and a taurate.

In another embodiment, the present invention provides a chemical washcomposition comprising water, a sulfonated bisulfite lignite, and ataurate.

The features and advantages of the present invention will be apparent tothose skilled in the art. While numerous changes may be made by thoseskilled in the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF DRAWINGS

These drawings illustrate certain aspects of some of the embodiments ofthe present invention, and should not be used to limit or define theinvention.

FIG. 1 compares filter cake removal properties vs. time of the removalsolution of the present invention and a prior art solution, as describedin Example 2.

While the present invention is susceptible to various modifications andalternative forms, a specific exemplary embodiment thereof has beenshown by way of example in the drawing and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the invention as defined by the appended claims.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to removing a fluid from a well bore witha chemical wash composition, and more particularly, to chemical washcompositions that comprise water, a sulfonated lignin, and a taurate.These chemical wash compositions may be used to at least partiallyremove or substantially displace a drilling fluid from a well bore. Asused herein, the term “remove” does not imply any particular degree ofremoval.

Among other things, the chemical wash compositions of the presentinvention may be used to at least partially remove a drilling fluid or afilter cake from a well bore surface. More preferably, the chemical washcompositions of the present invention may be used to at least partiallyremove a water-based drilling fluid or a filter cake from a well boresurface. Additionally, the chemical wash compositions generally shouldbe capable of water wetting a well bore surface.

In certain embodiments, the chemical wash compositions of the presentinvention comprise water, a sulfonated lignin, and a taurate. In dryembodiments, the chemical wash compositions of the present inventionwill substantially comprise a sulfonated lignin and a taurate. The dryform may be useful for transport to a well site. This may be lessexpensive than transporting liquid forms. The dry compositions may becombined with water or other base fluid at a well site, for instance, tobe used downhole. The term “dry,” as used herein, does not imply anyparticular degree of dryness.

If used, the water used in the chemical wash compositions of the presentinvention may include freshwater, saltwater (e.g., water containing oneor more salts dissolved therein), brine (e.g., saturated saltwaterproduced from subterranean formations), seawater, or combinationsthereof. The water may be from any source, provided that it does notcontain an excess of compounds that may adversely affect othercomponents in the chemical wash composition. Generally, the water may beadded in an amount such that the composition comprises about 30 to about50% active ingredients.

A sulfonated lignin is also included in the chemical wash compositionsof the present invention. The sulfonated lignin may be produced by thebisulfite process, i.e., a sulfonated bisulfite lignin, or be producedby sulfomethylation of a lignosulfonate with formaldehyde, i.e., asulfomethylated lignosulfonate. In some embodiments, the sulfonatedlignin may comprise a metal salt of the sulfonated lignin. A variety ofmetal salts of the sulfonated lignin may be used, including, but notlimited to, sodium salts, ammonium salts, potassium salts, calciumsalts, and combinations thereof.

A taurate is also included in the chemical wash composition of thepresent invention. Taurates are generally based on taurine, which isalso known as 2-aminoethanesulfonic acid. In certain embodiments,suitable taurates may have carbon chains in the range of from C₆ to C₁₈.Examples of suitable taurates include N-alkyl-N-acyl taurate, such asN-methyl-N-palmitoyl taurate, N-methyl-N-cocoyl taurate,N-methyl-N-oleyl taurate, and their lauroyl, myristoyl, and stearoylhomologs. An example taurate comprises N-methyl-N-cocoyl taurate. Insome embodiments, the taurate may comprise a metal salt of the N-alkyltaurate. A variety of metal salts of the taurate may be used, including,but not limited to, sodium salts, ammonium salts, potassium salts,calcium salts, and combinations thereof.

The sulfonated lignin and the taurate may be included in the chemicalwash composition in a sulfonated lignin-to-taurate volume ratio in therange of from about 5:1 to about 1:5, alternatively, in a sulfonatedlignin-to-taurate volume ratio in the range of from about 1:1 to about3:1, and alternatively, and possibly more preferably, in a sulfonatedlignin-to-taurate volume ratio of about 2:1. The sulfonated lignin andthe taurate may be included in the chemical wash composition in acombined amount in the range of from about 0.1% to about 5% by weight ofthe chemical wash composition, and alternatively in a combined amount inthe range of from about 1% to about 3% by weight of the chemical washcomposition. One of ordinary skill, with the benefit of this disclosureshould be able to determine the appropriate volume ratio and amount ofthe sulfonated lignin and taurate to include in the chemical washcompositions of the present invention.

Additional additives may be included in the chemical wash compositionsof the present invention as deemed appropriate by one skilled in theart. Examples of suitable additives include, but are not limited to,viscosifying agents such as clays, diatomaceous earth, starches,polymers, or mixtures thereof. Suitable viscosifying agents often arehydratable polymers that have one or more functional groups. Thesefunctional groups include, but are not limited to, hydroxyl groups,carboxyl groups, carboxylic acids, derivatives of carboxylic acids,sulfate groups, sulfonate groups, phosphate groups, phosphonate groups,and amino groups. The chemical wash composition may also include, butare not limited to, other surfactants such as nonylphenol ethoxylates,alcohol ethoxylates, alpha-olefinsulfonates, alkylpolyglycosides,alcohol sulfates, salts of ethoxylated alcohol sulfates, alkylamidoproply dimethylamine oxides, and alkene amidopropyl dimethylamineoxides.

Optionally, other additives may be added to the treatment fluids of thepresent invention as deemed appropriate by one skilled in the art withthe benefit of this disclosure. Examples of such additives include,inter alia, defoamers, curing agents, salts, corrosion inhibitors, scaleinhibitors, and formation conditioning agents.

The chemical wash compositions of the present invention may be used inany application in which it is appropriate or desirable to use such acomposition. In some embodiments, the chemical wash compositions of thepresent invention may be used to at least partially remove a drillingfluid from surfaces in a well bore. Such well bore surfaces may includethe exterior surface of a pipe string (if any) located in the well boreor the walls of the well bore. In some embodiments, the chemical washcomposition may remove at least a substantial portion of a drillingfluid from the well bore surfaces. Additionally, the chemical washcompositions also may remove at least a portion of a filter cake fromthe well bore surfaces. Additionally, the chemical wash composition mayalso be used to displace a drilling fluid located in the well bore, forexample, that at least partially fills an annulus between thesubterranean formation and a pipe string located in the subterraneanformation.

An example method of the present invention may comprise providing achemical wash composition of the present invention comprising water, asulfonated lignin, and a taurate, and contacting a well bore surfacewith the chemical wash composition to thereby at least partially removethe drilling fluid from the well bore surface. The contacting of thewell bore surface with the chemical wash composition may be static,dynamic, or intermittently static and dynamic. Factors such as viscosityof the fluid, pump rate of the composition, and hole geometry maydetermine the conditions at which the composition is delivered. As thoseof ordinary skill in the art may appreciate, in chosen embodiments, thechemical wash composition may be introduced into the well boreintermittently and at varying rates to enhance dispersion of thedrilling fluid and the filter cake into the chemical wash composition.In certain embodiments, the chemical wash composition may be introducedinto the well bore in turbulent flow. Additionally, the contacting ofthe well bore surfaces with the chemical wash composition further maycomprise introducing the chemical wash composition into the well bore soas to contact the well bore surfaces thereby at least partiallydispersing the drilling fluid and the filter cake into the chemical washcomposition. One of ordinary skill in the art with the benefit of thisdisclosure will recognize the appropriate conditions for deliverydictated by a desired use.

Additionally, in certain embodiments, the chemical wash composition maybe introduced into an annulus between a subterranean formation and apipe string located in the subterranean formation. In accordance withthe methods of the present invention, a cement composition may beintroduced into the annulus so that the chemical wash composition is atleast partially displaced from the annulus. Thereafter, the cementcomposition may be allowed to set. The cement composition may be anycement composition suitable for use in subterranean formation.Generally, the cement composition may comprise water and a cement, andoptionally any suitable additives.

Any cement suitable for use in the desired application may be suitablefor use in the cement compositions of the present invention. While avariety of cements may be suitable, in some embodiments, the cementcompositions of the present invention may comprise a hydraulic cement. Avariety of hydraulic cements may be utilized in accordance with thepresent invention, including, but not limited to, those that comprisecalcium, aluminum, silicon, oxygen, and/or sulfur, which set and hardenby reaction with water. Suitable hydraulic cements, include, but are notlimited to, Portland cements, pozzolana cements, gypsum cements, highalumina content cements, slag cements, and silica cements, andcombinations thereof. Another example of a suitable cement is “MICROMATRIX®” cement, which is commercially available from Halliburton EnergyServices, Duncan, Okla. Yet another example of a suitable cement is amixture of fly ash and lime.

Other additives suitable for use in subterranean operations may be addedto the cement compositions as desired. Suitable additives may includefly ash, pozzalonic additives, set retarders, fluid loss controladditives, surfactants, dispersants, micas, fibers, formationconditioning agents, bentonite, expanding additives, microspheres,weighting materials, defoamers, and the like.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

EXAMPLES Example 1

The following experiment was performed, inter alia, to determine theability of a mixture of bisulfite lignin salt and N-methyl-N-cocoyltaurate salt dissolved in water to remove water-based drilling fluid.

A cylinder of 1.9 inches in length and 1.6 inches in diameter formed ofa 60 mesh screen was attached over the sleeve of a Fann Model 35rotational viscometer having the Bob removed therefrom. The sleeve andthe cylindrical screen were weighed to obtain their initial weight, W₁.The cylindrical screen attached to the sleeve was immersed into theviscometer cup containing 10 pounds per gallon of water-based drillingfluid formed of calcium and magnesium silicate. The cylindrical screenattached to the sleeve was left in the drilling fluid under staticconditions for 10 minutes at room temperature. The sleeve andcylindrical screen were removed from the viscometer cup and a smooth,homogenous layer of drilling fluid was deposited on the cylindricalscreen. The sleeve and screen were left for 2 minutes so that any excessdrilling fluid dripped off. Thereafter, the bottom surface was gentlywiped off using a paper towel. The sleeve, the screen, and the drillingfluid thereon were weighed, W₂. The weight of the drilling fluiddeposited (W₃) was W₃=W₂−W₁. The cylindrical screen attached to thesleeve and coated with the drilling fluid was dipped into the viscometercup containing the water-based drilling fluid removal solution of thisinvention having a concentration of bisulfite lignin salt andN-methyl-N-cocoyl taurate salt in a 2 to 1 ratio. The sleeve and thecylindrical screen attached thereto were rotated at 170 rpm for 15minutes and then taken out of the drilling fluid removal solution.Excess solution was allowed to drip for 2 minutes and the bottom waswiped off gently with a paper towel. The sleeve and screen were weighed,W₄. The amount of water-based drilling fluid removed by the removalsolution in 15 minutes was W₃-W₄. The test was repeated on the drillingfluid removal solution of this invention.

The water-based drilling fluid removal solution of this invention wasreplaced by a prior art water-based drilling fluid removal solutioncomprised of kraft lignin salt and sodium salt of N-methyl-N-oleyltaurine in a 2 to 1 ratio. This prior art drilling fluid removalsolution is utilized for removing water-based drilling fluids from alltypes of formations. The above described experiment was repeatedutilizing the prior art drilling fluid removal solution. A comparison ofthe drilling fluid removal properties of the removal solution of thisinvention and the prior art solution are set forth in Table I below.

TABLE I % Mud Removed in 15 min. at 170^(sec−1) Prior Art Solution 10.85Bisulfite Lignin (Test 1) 11.39 Bisulfite Lignin (Test 2) 11.01

Example 2

The following experiment was performed to determine the ability of amixture of bisulfite lignin salt and N-methyl-N-cocoyl taurate saltdissolved in water to remove water-based drilling fluid.

A Model 90 Dynamic Filtration Device developed by Fann Instruments, Inc.(a Halliburton Company) was used to compare a solution of bisulfitelignin salt and N-methyl-N-cocoyl taurate salt in a 2 to 1 ratio to MudFlush (prior art solution) in removing a filter cake of simple bentonitemud. Mud Flush is a mixture of water, an anionic-nonionic surfactantblend, and sodium acid pyrophosphate, and is commercially available fromHalliburton Energy Services. The test procedure for this experiment isoutlined in SPE 84560 of the Society of Petroleum Engineers AnnualTechnical Conference and Exhibition in Denver, Colo. 5-8 Oct. 2003. Whena filter-cake of simple bentonite mud was exposed to the newformulation, it took approximately 300 minutes of exposure before enoughof the filter-cake was removed to allow dissipation of the entire fluidvolume through the filter cake and simulated core. This compares to over370 minutes that were required for the same volume of Mud Flush to passthrough an identical filter cake and core. A comparison of the drillingfluid removal properties of the removal solution of this invention andthe prior art solution is set forth in FIG. 1.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. In particular, every range of values(of the form, “from about a to about b,” or, equivalently, “fromapproximately a to b,” or, equivalently, “from approximately a-b”)disclosed herein is to be understood as referring to the power set (theset of all subsets) of the respective range of values, and set forthevery range encompassed within the broader range of values. Also, theterms in the claims have their plain, ordinary meaning unless otherwiseexplicitly and clearly defined by the patentee.

1. A chemical wash solution comprising: water, a sulfonated bisulfitelignin, and a taurate, wherein the sulfonated bisulfite lignin and thetaurate are present in the chemical wash solution in a combined amountin the range of from about 0.1% to about 5% by weight of the chemicalwash solution.
 2. The chemical wash solution of claim 1 wherein thechemical wash solution further comprises an additive chosen from thefollowing group: viscosifying agents, emulsion forming agents,diatomaceous earth, starches, polymers, defoamers, curing agents, salts,corrosion inhibitors, scale inhibitors, formation conditioning agents,and mixtures thereof.